The Basics: Everything You Need to Know about CNC Machining

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CNC machining is a subtractive manufacturing method, which can create accurate, high-quality parts with elegant finishes. A final product is created from a large block, through material removal method. CNC machining uses computers to control machine tools for manufacturing purposes.

Tools that can be managed this way include lathes, mills, routers and grinders. CNC services include milling, turning, EDM, wire EDM and surface grinding etc.

What is CNC prototyping and low volume production?

Low-volume production is termed as manufacturing of mass-production quality parts in a small volume of 50 to 100,000 parts. The most common way used for prototyping and low volume production is CNC machining. Prototyping and low volume production is being done by different CNC milling, turning and surface treatment processes. This type of machining is different from regular volume production strategies.

Why Choose CNC-based low volume production and prototypes?

Some advantages of CNC prototypes and low volume production are:

– The mechanical properties of CNC-machined parts are extremely similar to the properties of injection molded parts.
– It can work with common material like aluminum, creating a prototype which is much cheaper than 3D printing.
– Makes it possible to launch your product in market as quickly as possible.
– Saves money instead of investing in mass production.
– Allows flexibility in design changing after modifications.
– Suitable for test runs.

Applications:

– Custom CNC machined parts
– Quality customized products
– Plastic injection molded parts
– Bridge production
– Functional prototypes
– Pre-production components for verification tests

The CNC Machining Process:

Before machining, a CAD file is created (2D or 3D) and then the code is created which can be understood by the CNC machine. The program is then loaded to the machine computer and the operator runs a test program to ensure there are no problems. This trail run is referred as “cutting air”. After it the operate push the start button and the working of machine is started according to the given instructions, operator needs to check time-to-time that the machine is working properly. At last, the finished part is produced.

Where can you find CNC machining services?
CNC prototyping and low volume production is done by CNC machines in CNC machine shops. Some of the most commonly used machines are;
– CNC milling
– CNC turning
– EDM and EDM wire cut.

CNC Milling

A computer-guided tool is used to remove material from a larger block in order to produce parts. It can be done on 2-axis to 5-axis CNC machines depending upon the complexity of the part. In CNC milling the tool is moved perpendicularly to the workpiece.

CNC milling

A CNC mill is not suitable for making holes; it is used to remove material from the workpiece.

What are CNC milling tools?
There are different types of milling tools for axial and lateral cutting;
Axial cutting: The tool having teeth on the tip of the cutting head is used for axial cutting.
Lateral cutting: The tool having teeth perpendicular to the circular cutting head is used for lateral cutting.

What are Pros and Cons of CNC milling?

There are some advantages and disadvantages of CNC milling machines:

Pros:
– High accuracy: tight tolerance of .001″ to .003″.
– Speed: CNC mills are much quicker than hand milling machine.
– CAD Integration: It requires CAD file to produce parts which lead to the fast and easy prototyping.

Cons:
– Expensive: CNC mills are very expensive to purchase.
– Maintenance: It must be rigorously maintained.

CNC Turning

CNC turning produces parts by removing material from a rotating workpiece which is mounted on a chuck, by moving tool parallel to the workpiece. It produces prototypes with round cross-sections.

CNC turning

Cutting tool movement:
The cutting tool can move axially in 2 ways;
Motion along the side of the part
To and fro motion.

What are Pros and Cons of CNC turning?
There are some advantages and disadvantages of CNC turning machines;
Pros:
– Fast and Easy: It is the fast and easy process to create a prototype.
– Efficiency: As it is completely computer controlled process it will provide accurate and high-quality parts.
– Easy Upgrade: Only a software update is required to upgrade the machine.
– Resize: CNC turning can be used for reducing length and diameter of the worpiece.

Cons:
– Expensive Machine: CNC turning machines are very expensive to purchase.
– Tool Crashing: Tool crashing or breaking may happen frequently due to high wear and frictional effect.
– Skilled Labor: Skilled workers are required to operate the machines.

Electric Discharge Machining (EDM)

In electrical discharge machining, or EDM, the material is removed from a workpiece using thermal energy. It does not need any other mechanical force in the removal process.

EDM working

How does EDM work?
EDM is a manufacturing process that removes material from conductive materials using an electrode. In a small gap between workpiece and electrode, a discharge occurs that removes material through melting or vaporizing. For this process, the electrode and the workpiece have to be submerged in a dielectric fluid.

What is EDM wire cut?
EDM wire cut is also known as wire erosion, or spark EDM. In it a thin wire is used to cut the workpiece. Wire EDM is able to cut metals as thin as 0.004”.

EDM Wirecut

How does EDM wire cut work?
In it the wire acts as a electrode, the wire constantly coming from an automated feed with a spool. The wire produces a discharge which results in material removal through melting or vaporizing. The thin wire allows precision cuts, with a positioning accuracy of +/- 0.0002” and three inches wide kerfs.

EDM Wirecut Working Process
What are Pros and Cons of EDM/EDM wire cut?
There are some advantages and disadvantages of EDM/EDM wire cut machines.

Pros:
– Tolerances: Tolerances of +/- 0.005 can be achieved.
– Material Effect: Material density does not affect the process.
– Complex shapes: Allows cutting of complex shapes.
– Excellent finishing: EDM process leaves no rough edges.

Cons:
– Material limitation: Only able to machine conductive materials.
– Expensive: More expensive process than milling or turning.
– Time consuming: It takes more time as compared to other methods.

Outlined above are some of the technologies being used by the CNC machine shops providing CNC machining services, including CNC prototyping and low volume production with their advantages and applications. We also discussed different machining operations such as CNC milling, CNC turning, EDM and EDM wire cut, mentioned their working principles which are different for every operation and discussed the pros and cons of each above mentioned machining operations. This should help you make a decision about the best options for your business.

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Matthew Miller

Matt Miller is a partner and contributing editor at B2B News Network.